Recent years have witnessed practical use of a flat-panel display in various products and fields. This has led to a demand for a flat-panel display that is larger in size, achieves higher image quality, and consumes less power.
Under such circumstances, great attention has been drawn to an EL display device that (i) includes an EL element which uses electroluminescence (hereinafter abbreviated to “EL”) of an organic or inorganic material and that (ii) is an all-solid-state flat-panel display which is excellent in, for example, low-voltage driving, high-speed response, and light-emitting characteristics.
In order to achieve a full-color display, an EL display device includes a luminescent layer which outputs light of a desired color in correspondence with a plurality of sub-pixels constituting a pixel.
A luminescent layer is formed as a vapor-deposited film on a film formation target substrate (this substrate hereinafter also referred to simply as a “target substrate”). Specifically, in a vapor deposition process, a fine metal mask (FMM) having high-precision apertures is used as a vapor deposition mask, and differing vapor deposition particles are vapor deposited to each region of the target substrate.
In order to achieve a high-resolution EL display device, it is necessary to deposit the vapor deposition particles onto the target substrate with a high level of precision.
FIG. 12 and FIG. 13 are each a cross-sectional view of a target substrate and a vapor deposition mask, each figure being for explaining problems occurring with a conventional vapor deposition method. Note that in FIG. 12 and FIG. 13, dotted-line arrows represent paths of vapor deposition particles.
Conventionally, vapor deposition is generally carried out while the target substrate and the vapor deposition mask are caused to be in close contact. In a case (i) where a target substrate 305 and a vapor deposition mask 301 become separated, as illustrated in FIG. 12, and (ii) a vapor deposition particle enters and passes through an aperture 303 from an angle, with respect to the surface of the vapor deposition mask 301, which angle is smaller than a given angle, the vapor deposition particle is deposited in a region outside a sub-pixel region P. As a result, a vapor deposition region V becomes larger than the sub-pixel region P, and a luminescent layer 310 is formed in a manner so as to expand wider than the sub-pixel region P.
Furthermore, in a case where (i) vapor deposition particles are emitted from a vapor deposition source 307 which is not positioned opposite to an aperture 303, as illustrated in FIG. 13, and (ii) a vapor deposition particle enters and passes through the aperture 303 from an angle, with respect to the surface of the vapor deposition mask 301, which angle is smaller than a certain angle, the vapor deposition particle is deposited at a position out of alignment with the sub-pixel region P. As a result, the luminescent layer 310 is formed out of alignment with the sub-pixel region P.
In this way, performing vapor deposition while the target substrate 305 and the vapor deposition mask 301 are separated from each other causes a marked reduction in the precision of the vapor deposition pattern. As such, in order to avoid a reduction in the precision of the vapor deposition pattern, it is necessary to carry out vapor deposition while the target substrate 305 and the vapor deposition mask 301 are in a state of close contact.
In a conventional vapor deposition process, a vapor deposition mask is attached evenly to a frame via strong tension, and, in a vapor deposition device, the vapor deposition mask is caused to come into close contact with a substrate via a mechanical means.
With merely a mechanical means, however, factors such as a lack of device precision and the introduction of a foreign object make it impossible to ensure an adequate degree of contact between the target substrate and the vapor deposition mask. Note that, conventionally, a vapor deposition mask is generally made from a metal material.
In recent years, in order to address this issue, a method to ensure close contact between a mask and a target substrate has become commonly employed, specifically a method in which a magnetic force generating source, such as a magnet or electromagnet, is provided on a substrate holder side of a vapor deposition device, and the vapor deposition mask is magnetically attracted toward the substrate holder side.
At the same time, in recent years, vapor deposition masks have been proposed in which a mask substrate (mask base material) thereof is made by using non-metallic materials, such as resin or ceramic materials. Using such materials in the mask substrate makes it possible to form high-precision apertures in the mask substrate by use of, for example, laser processing. As such, using a vapor deposition mask made from such materials makes it possible to increase the precision of the vapor deposition pattern. However, since such materials are not magnetic, they do not allow a vapor deposition mask and a target substrate to be brought into close contact via magnetic force.
In attempting to address this, Patent Literature 1 discloses a vapor deposition mask including (i) a metallic mask having a plurality of rows of slits and (ii) a resin mask laminated to the metallic mask, which resin mask has apertures provided at positions coinciding with the slits.
According to Patent Literature 1, the vapor deposition mask including the metallic mask and the resin mask makes it possible to carry out deposition through high-precision apertures formed in the resin mask while also causing the target substrate and the vapor deposition mask to be in close contact via magnetic force.